Vibrational structure, spin-orbit splitting, and bond dissociation energy of Cl2+(X̃Πg2) studied by zero kinetic energy photoelectron spectroscopy and ion-pair formation imaging method

Abstract

The isotopomer-resolved vibrational and spin-orbit energy structures of Cl(2) (+)(X (2)Pi(g)) have been studied by one-photon zero kinetic energy photoelectron spectroscopy. The spin-orbit energy splitting for the ground vibrational state is determined as 717.7+/-1.5 cm(-1), which greatly improves on the accuracy of the previously reported data. This value is found to be in good agreement with the ab initio quantum chemical calculation taking account of the inner shell electron correlation. The first adiabatic ionization energy (IE) of Cl(2) is determined as 92 645.9+/-1.0 cm(-1). Using the ion-pair formation imaging method to discriminate signals of Cl(+)((1)D(2)) from those of Cl(+)((3)P(j)), the threshold for ion-pair (E(tipp)) production, Cl(+)((1)D(2))+Cl(-)((1)S(0))<--Cl(2)(X (1)Sigma(g) (+)), is determined as 107 096(-2) (+8) cm(-1). By using the determined IE and E(tipp) for Cl(2) and also the reported IE and electronic affinity for chlorine atom, the bond dissociation energies of Cl(2)(X (1)Sigma(g) (+)) and Cl(2) (+)(X (2)Pi(g)) have been determined as 19 990(-2) (+8) and 31 935.1(-2) (+8), respectively.

Multiconfigurational study on the synchronous mechanisms of the ClO self-reaction leading to Cl or Cl2

“…The CASPT2 sum energy value of -1.30 eV for Cl 2 (X 1 R g -) ? O 2 (X 3 R g -) is in good agreement with the experimental sum energy values of -1.31 eV [43]. The previously reported CAS-CI sum energy value (0.76 eV) [27].…”

“…For example, the sum energy of the reactant group = 2 9 the calculated total energy value of ClO (X 2 P) at its optimized geometry minus the calculated total energy value of ClOOCl (1 1 A) at its optimized geometry. The previously reported experimental [2,7,20,43] and theoretical [25,27] sum energy values (relative to 1 1 A) are listed in Table 3. The CASPT2 sum energy value of 0.70 eV for ClO (X 2 P) ?…”

The X+ 2Πg, A+ 2Πu, B+ 2Δu, and $\mathrm{a}^+\ ^4\Sigma _{\mathrm{u}}^-$a+Σu−4 electronic states of ${\rm Cl}_2^+$ Cl 2+ studied by high-resolution photoelectron spectroscopy

“…These studies indicated that a broad range of vibrational levels of the X + and A + states could be studied (σ g ) 2 (π u ) 4 (π * g ) 3 X + 2 g (σ g ) 2 (π u ) 3 (π * g ) 4 A + 2 u (σ g ) 1 (π u ) 4 (π * g ) 4 2 + g (σ g ) 2 (π u ) 4 (π * g ) 2 (σ * u ) 1 4 − u , 2 u , 2 − u , 2 + u at high resolution by pulsed-field-ionization zero-kineticenergy (PFI-ZEKE) photoelectron spectroscopy and that information on the mechanisms leading to ion-pair formation in the photoionization of Cl 2 might be obtained from such studies. PFI-ZEKE photoelectron spectra of the low vibrational levels (v + ≤ 6) of the X + state with partial rotational resolution were reported by Li et al 9 who also determined precise values of the first adiabatic ionization energy of Cl 2 and of the threshold for Cl + ( 1 D 2 ) + Cl − ( 1 S 0 ) ion-pair formation. A recent high-resolution measurement of the threshold ion-pairformation spectrum of Cl 2 19 near the Cl + ( 3 P J , J = 0 − 2) + Cl − ( 1 S 0 ) thresholds led to the observation of ion-pair states of very high principal quantum numbers (≥1800) and to the observation of interactions between series of ion-pair states converging to different ion-pair dissociation thresholds.…”

“…9. The band centersν 0v + derived from the analysis of the rotational structure are listed in Tables II and III and formed …”

“…Table I lists the configurations that need to be considered in the region up to 3 eV of internal energy, which is at the focus of the present article, and the corresponding electronic states. Experimental information on the rovibrational and spin-orbit energy level structure of several of these low-lying states has been obtained by photoelectron spectroscopy [4][5][6][7][8][9] and by optical spectroscopy. 2,3,[10][11][12][13][14][15][16] At low resolution, the He I photoelectron spectrum reveals a very simple structure with three main bands centered at ≈11.8, 14.3, and 16 eV, which correspond to three S = 1/2 cationic states that are formed from the (σ g ) 2 (π u ) 4 (π * g ) 4 X 1 + g ground state of Cl 2 by (π * g ) −1 , (π u ) −1 , and (σ g ) −1 single-photon ionization.…”